JP2005067192A - Recording medium for ink and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make both image saving properties for a longer period and recording characteristics compatible, and to surely perform these characteristics. <P>SOLUTION: When a coloring material deterioration proofing material is incorporated into an ink receiving layer by coating the ink receiving layer with a coating liquid in which the coloring material deterioration proofing material is dissolved in a solvent, the ink receiving layer comprises a high concentration site containing the coloring material deterioration proofing material at a high concentration, and a low concentration site containing the coloring material deterioration proofing material at a low concentration, and the high concentration site is positioned on the recording face side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides a recording medium suitable for recording using water-based ink and a method for producing the same. In particular, the present invention relates to an ink recording medium having long-term image storability and a method for producing an ink recording medium capable of reliably realizing this characteristic.

  Ink-jet recording methods use microscopic droplets of a recording liquid (recording liquid) such as ink to fly according to various operating principles and adhere to a recording medium such as paper (also referred to as a recording medium). It has features such as high-speed, low-noise, easy multi-coloring, large recording pattern flexibility, and no development required. Further expansion to output units in information devices such as machines, word processors, facsimile machines, plotters, etc., has been rapidly spreading. In recent years, high-performance digital cameras, digital videos, scanners, etc. are being offered at low cost, and coupled with the widespread use of personal computers, printers that employ inkjet recording methods for the output of image information obtained from them are extremely suitable. It has come to be used. In such a background, it has been required to easily output an image that is inferior to that of silver salt photography or plate-making multicolor printing by an inkjet recording method.

  In order to satisfy these requirements, improvements have been made to the structure and recording method of the printer itself, such as higher speed recording, higher definition, and full color, and improvements to the structure and characteristics of the recording medium have been actively studied. ing.

  Various types of recording media used for inkjet recording and the like have been proposed. A recording medium comparable to a silver salt-based photograph is required to have excellent dye coloring properties, high surface glossiness, and image formation having high resolution. As a constituent material of an ink receiving layer of a recording medium capable of providing an image comparable to a silver salt photograph, for example, alumina hydrate can be mentioned, and described in JP-A-7-232475 (Patent Document 1). There is.

  Furthermore, recently, the storability of recorded images has been required. In order to improve light resistance and gas resistance, a method for improving the storage stability of a recorded image including a color material deterioration preventing material has been proposed. For example, a recording sheet containing a cationic compound has been proposed in order to solve a migration phenomenon in which an obtained image blurs due to a color material moving due to the influence of temperature and humidity.

  Japanese Patent Publication No. 4-34512 (Patent Document 1) discloses a method for improving image light storage stability by adding a hindered amine compound as an acid salt to a coating liquid for forming ink jet recording paper. JP-A-3-13376 (Patent Document 2) discloses a recording medium material in which a hindered amine and a hindered phenol dissolved in an organic solvent are applied. Certainly, recording media containing such colorant deterioration preventing materials exhibit a certain degree of effect on gas resistance and light resistance, but in many cases they are not yet at a satisfactory level for long-term image storage stability.

  Japanese Patent Laid-Open No. 2001-162928 (Patent Document 3) is known as this prior art level. Here, with respect to the ink receiving layer itself having a thickness of 35 μm provided on the film, the upper part 5 μm (the part from the surface to a depth of 5 μm) and the lower part 5 μm (the thickness 5 μm upward from the interface with the film) The amount of nitrate groups contained in them is compared. As a comparison result, the lower 5 μm is smaller than the upper 5 μm, but the effect is only “light resistance” due to the presence of nitrate group. That is, it is only described that this effect is effective for a comparative example that does not contain any nitrate group. In addition, this document discloses that a large amount of coating liquid is applied to a recording material. However, how the material for supplying nitrate groups is absorbed in the ink receiving layer, the coating liquid is used. There is no disclosure of how the ink-receiving layer after application was dried. In addition, this document does not disclose even a method for detecting this nitrate group, and cannot be reexamined. In particular, the distribution state of nitrate groups in the ink receiving layer region between the upper 5 μm portion and the lower 5 μm portion is completely unknown.

  Further, JP 2000-2111246 A (Patent Document 4) discloses an inkjet recording paper in which aluminum nitrate is internally added and uniformly dispersed. Patent Document 4 describes that a recording paper having aluminum nitrate is excellent in light resistance. Comparing the light resistance described in Patent Document 3 and Patent Document 4, it is impossible to say unconditionally because the test method is different. However, the light resistance of the comparative example of Patent Document 3 is at a level where there is no problem in Patent Document 4. From the above, it is estimated that the light resistance of the example described in Patent Document 3 is weaker than the recording medium in which the aluminum nitrate of Patent Document 4 is internally added and uniformly dispersed. This suggests that the intermediate 25 μm range is uniform.

On the other hand, JP-A-2001-010214 (Patent Document 5) discloses an ink receiving layer having a three-layer structure in which a predetermined nitrogen compound is uniformly contained and a coating solution containing silica, polyvinyl alcohol and boric acid is applied by 70 μm. doing.
Japanese Patent Publication No. 4-34512 Japanese Patent Laid-Open No. 3-13376 JP 2001-162928 A JP 2000-2111246 A Japanese Patent Laid-Open No. 2001-010214

  In the present invention, how to effectively use a coloring material deterioration preventing material (preferably a gas deterioration preventing material such as a hindered amine that mainly prevents the coloring material from being destroyed by a gas containing ozone) that could not be achieved by the prior art. The goal is to solve the technical problem that can be achieved. This is because the type in which the color material deterioration preventing material is mixed in advance in the coating liquid only provides a uniform distribution as shown in FIG. 1, and therefore the color necessary for the entire ink receiving layer to obtain desired characteristics. In order to secure the concentration of the material deterioration preventing material, it is necessary to add a large amount of the color material deterioration preventing material. However, the addition of a large amount of such a color material deterioration preventing material causes a new problem that the ink absorbability of the ink receiving layer is deteriorated. On the other hand, when trying to increase the ink absorbability, naturally, the color material deterioration preventing material must be reduced. In addition, when the base material of the recording medium has an absorptivity, that is, an absorbability of the coating liquid, the coating liquid containing the color material deterioration preventing material is sufficient to reach the base material even if the color material deterioration preventing material is externally added. As shown in FIG. 2, the color material deterioration preventing material penetrates to the base material. Therefore, an effect corresponding to the amount of the external addition cannot be obtained, and the color material deterioration preventing material is wasted. Therefore, a sufficient effect cannot be expected even in the external addition method.

  Therefore, the present inventors have further intensively studied in order to obtain an ink receiving layer excellent in ink absorbency while achieving an effect more than that with respect to the amount of the coloring material deterioration preventing material to be provided. As a result, when examining the behavior of the coating liquid containing the ink and the coloring material deterioration preventing material in the depth direction from the recording surface of the ink receiving layer, the state where the ink itself permeates and diffuses, the diffusion distribution state of the coloring material, Is taken into consideration, the color material exists within a range up to a depth of 30 μm when viewed from the recording surface, and more importantly, it has a color material distribution within a range up to a depth of 20 μm. Therefore, the inventors have found that the presence of a color material deterioration preventing material corresponding to these color material distributions is an important factor for increasing the efficiency of the effect. Furthermore, it was found that the distribution of the color material deterioration preventing material in the ink receiving layer does not impair the ink absorbability, and it is important to obtain the desired color material deterioration preventing effect with as little amount as possible. .

  Accordingly, the first problem of the present invention is that the ink receiving layer (preferably the concentration of the coloring material deterioration preventing material on the recording surface) can exhibit the effect of the given amount of the coloring material deterioration preventing material much more efficiently than the conventional one. The second problem is to provide an ink receiving layer that achieves both effective use of the colorant deterioration preventing material and good ink absorption. It is to solve the third problem of how to manufacture the ink receiving layer of the second problem or the second problem.

  A first invention of the present invention is an ink recording medium comprising an ink receiving layer comprising a pigment for holding a color material of an ink, a binder for the ink, and a color material deterioration preventing material, which constitutes a recording surface. The ink receiving layer is within a range from the recording surface side to 30 μm in the depth direction, and the coloring material deterioration preventing material has a relatively high density part and a relatively low density part. And the high density part is located closer to the recording surface than the low density part.

  A second invention of the present invention has the configuration of the first invention described above, and further, the concentration of the colorant deterioration preventing material is within the range of the upper region from the recording surface of the ink receiving layer to a depth of at least 15 μm. Is a recording medium for ink having a density distribution that decreases in the depth direction from the recording surface.

  A third invention of the present invention has the configuration of the first and second inventions described above, and further within the thickness range of 10 μm arbitrarily selected in the depth direction in the upper region, the color material This is a recording medium for ink having a density distribution in which the density of the deterioration preventing material decreases from the recording surface in the depth direction.

  A fourth invention of the present invention has the configuration of the first and second inventions described above, and further within the thickness range of 5 μm arbitrarily selected in the depth direction in the upper region, the color material This is a recording medium for ink having a density distribution in which the density of the deterioration preventing material decreases from the recording surface in the depth direction.

  According to a fifth aspect of the present invention, there is provided a method for producing an ink recording medium comprising an ink receiving layer comprising a pigment for forming a recording surface and holding an ink color material, a binder for the pigment, and a color material deterioration preventing material. In the method, the color material deterioration preventing material includes a high density part having a relatively high density and a low density part having a relatively low density in the depth direction from the recording surface side of the ink receiving layer, and the high density A method for producing a recording medium for ink, comprising the step of forming, in the ink receiving layer, a concentration distribution of the colorant deterioration preventing material, the portion of which is located closer to the recording surface than the low concentration portion. is there.

  According to a sixth aspect of the present invention, there is provided an ink recording medium comprising an ink receiving layer comprising a pigment for holding a color material of ink, a binder for the ink, and a color material deterioration preventing material. In the production method, a step of forming a wet surface containing a cross-linking agent that cross-links the binder on a base material, and applying a coating liquid containing the pigment and the binder to the wet surface on the base material to receive ink A step of forming a layer, a step of applying a coating liquid containing the colorant deterioration preventing material from the surface of the ink receiving layer, and a step of applying a coating liquid containing the colorant deterioration preventing material And a step of forming a distribution of the deterioration preventing material by drying, and a method for producing a recording medium for ink.

  According to the first aspect of the present invention, the ink receiving layer capable of exhibiting the effect of the given amount of the color material deterioration preventing material far more than the conventional one and the effective use of the color material deterioration preventing material and good ink absorption are compatible. An ink receiving layer can be provided to achieve. According to the second aspect of the present invention, since the distribution is further on the recording surface side, the absorption efficiency can be increased and the effect of the color material deterioration preventing material can be further improved. Further, according to the third aspect of the present invention, a substantially steep distribution can be formed, so that the absorption efficiency and the distribution of the colorant deterioration preventing material can be brought into an ideal state. In particular, when the condition of the second invention is premised, it becomes even better. Similarly, the fourth aspect of the present invention is in an ideal state, so that the effects described in the following embodiments can be reliably obtained. According to the fifth and sixth aspects of the present invention, the ink receiving layers of the first to fourth aspects can be more reliably produced.

  In the present invention, the color material deterioration preventing material (particularly preferably, the gas deterioration preventing material such as hindered amine that mainly prevents the color material from being destroyed by the gas containing ozone) is uniformly distributed in the ink receiving layer. The color material deterioration preventing material is within a range from the recording surface side of the ink receiving layer to 30 μm in the depth direction. Long-term image storability can be achieved by a configuration in which the higher density part including the lower part is located on the recording surface side than the lower density part where the density of the colorant deterioration preventing material is lower. As shown in FIG. 3, when there are many color material deterioration preventing materials in the ink receiving layer on the recording surface side of the ink receiving layer, when the ink is printed on this recording medium, the color material deterioration preventing material is present in the vicinity of the dye. Since there are many materials, the effect of the color material deterioration preventing material can be sufficiently exerted compared with the case where the color material deterioration preventing material is uniformly distributed in the ink receiving layer. Further, when dyes are present at a position deeper than 30 μm in the depth direction from the recording surface side of the ink receiving layer, these dyes may hardly affect image characteristics such as optical density and color. Many. Therefore, the concentration distribution of the color material deterioration preventing material is preferably within a range of 30 μm from the recording surface side of the ink receiving layer to the depth direction.

  In particular, at a position from the recording surface of the ink receiving layer to 15 μm in the depth direction, the concentration of the colorant deterioration preventing material has a concentration distribution that decreases from the recording surface of the ink receiving layer in the depth direction. Then, since the color material deterioration preventing material exists so as to learn the penetration of the dye, the effect can be further exhibited. That is, in the present invention, it is important to have a density distribution in the vicinity of the recording surface, that is, in the upper layer portion as viewed from the recording surface side of the ink receiving layer.

  The concentration distribution of the colorant deterioration preventing material here is measured as follows. The cross section of the ink recording medium is subjected to line analysis by FT-IR microscopic transmission measurement, and the absorbance of one or a plurality of absorption wavelengths capable of determining the colorant deterioration preventing material is shifted by 1 μm in the depth direction as will be described later. Measured and determined. A concentration distribution was determined from the obtained absorbance change.

  The ink recording medium of the present invention can be manufactured by the following manufacturing method. First, an ink receiving layer containing at least a pigment for holding an ink coloring material and a binder for the pigment is provided so as to have a binder layer that has been cross-linked in the depth direction from the recording surface side. A coating liquid containing a coloring material deterioration preventing material is applied to the ink receiving layer and immediately dried to obtain a concentration distribution in which there are many coloring material deterioration preventing materials on the recording surface side of the ink receiving layer. It is possible to easily manufacture an ink recording medium. The reason for having such a concentration distribution is not clear, but the present inventors presume as follows.

  When a coating liquid containing a colorant deterioration preventing material is applied to a recording medium having a binder layer that has been cross-linked in the depth direction from the recording surface side of the ink receiving layer, the colorant deterioration preventing material is As it penetrates in the depth direction in the state of being contained in the solvent, it is stopped by the crosslinked binder and does not penetrate so much into the substrate side of the ink receiving layer, so that a large amount exists in the ink receiving layer. If the solvent that dissolves the color material deterioration preventing material is evaporated from the ink receiving layer by a rapid drying process while the color material deterioration preventing material does not completely permeate, the color material deterioration preventing material is accompanied by the evaporated solvent. Are pulled up in the direction of the recording surface and gather on the recording surface side. Therefore, it seems that the density distribution which exists abundantly on the recording surface side of the ink receiving layer can be provided. Therefore, the following two points play an important role in achieving the object of the present invention. That is, the first point is to suppress the permeability of the color material deterioration preventing material by controlling by crosslinking of the binder, and the second point is that the color material deterioration preventing material is applied after the color material deterioration preventing material is applied. It is important to move to the drying process within a short time that does not penetrate completely.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. As a preferable manufacturing process of the ink recording medium of the present invention, there are roughly three forms shown in FIGS. FIG. 4 includes a two-step surface treatment step, an ink receiving layer forming step, and a color material deterioration preventing material external addition step. 5 and 6 show a method for producing a recording medium for ink including a casting step for imparting surface glossiness, but the external addition step of the colorant deterioration preventing material may be performed either before or after casting. From the viewpoint of the appearance of the ink recording medium in the post-finishing process, it is preferable to add a color material deterioration preventing material before casting.

  A preferred embodiment of a method for manufacturing an ink recording medium in an embodiment relating to an ink receiving layer will be described. In the production method of the present invention, the proper coagulation action of the pigment and the binding action of the binder are mainly at the liquid-liquid interface between the two coating liquids for forming two layers that are laminated one above the other. Since it can be reliably obtained while taking advantage of the state of the coating liquid and the loss of the binder that should be in the ink receiving layer to the inside of the substrate can be prevented, the characteristics of the ink receiving layer are stabilized and its productivity is good It is. The recording medium for ink of the present invention has a novel structure obtained as a result because the amount of the binder that should be in the ink receiving layer can be secured in the ink receiving layer. That is, in a preferred embodiment according to the present invention, the ink receiving layer has a first layer region in which the binder is made relatively uniform with respect to the pigment, and the binder is cross-linked by the second cross-linking agent compared to the first layer region. A second layer region that is cross-linked so as to increase the degree, and the first layer region is located closer to the recording surface that receives ink than the second layer region. A recording medium is preferable.

  The recording medium of the present invention can be obtained by applying a coating liquid containing a colorant deterioration preventing agent to such an ink receiving layer and drying it immediately.

  The ink receiving layer of the recording medium for ink includes a first layer region in which the binder is cross-linked by the first cross-linking agent and is made relatively uniform with the pigment, and the binder is a first layer by the second cross-linking agent. A second layer region that is crosslinked so that the degree of crosslinking is greater than that of the region, and the first layer region is located closer to the ink recording surface than the second layer region.

  The degree of cross-linking is the relative quantity difference or quantity ratio (for example, twice or more) of common elements contained in the first and second layer regions of the common elements of the first and second cross-linking agents. Can be judged. In addition, as a specific material and production method thereof, for example, a coating liquid obtained by dissolving and mixing alumina hydrate as the pigment, polyvinyl alcohol as the binder, and orthoboric acid as the first crosslinking agent, It is mentioned that the recording medium for ink is formed by coating on the wet surface of a base material containing tetraborate as the second cross-linking agent for forming the second layer region. it can. Furthermore, in this coating solution, it is mentioned as a practical example that the content per unit area of the orthoboric acid is less than the content per unit area of the sodium tetraborate contained in the wet surface. Alternatively, the pigment is alumina hydrate, the binder is polyvinyl alcohol, the first and second crosslinking agents contain the same boron “B”, and the boron “B” contained in the second layer region. More preferably, the amount is at least twice the amount of boron “B” contained in the first layer region.

In such a method for producing an ink recording medium related to an ink receiving layer, the surface of the substrate is subjected to a certain degree of wetness (coating liquid state or thickened state) after the surface treatment with the second crosslinking agent is performed on the substrate. However, it is preferable that a coating liquid containing a first cross-linking agent for forming the next ink receiving layer is applied while this state is maintained. Solids content and coated amount of the coating solution used in the surface treatment step, for example, preferably so as to be 0.05 g / m ² or more 2.0 g / m ² or less of the dry coating amount in terms of solid content . In addition, when the above range is not satisfied, the viscosity of the coating liquid is too low and the liquid flow is large. When the above range is exceeded, in the casting process, a point-like surface (cast surface) defect is likely to occur. In some cases, a uniform and good glossy surface cannot be obtained. By applying the coating liquid in a state where the substrate surface is in a certain wet state, a reaction state at the liquid-liquid interface is ensured between the coating liquid and the second cross-linking agent. That is, at this interface, the gelation rate or the crosslinking rate of the ink-receiving layer coating solution is increased, and the first layer region in which the binder is crosslinked by the first crosslinking agent and is made relatively uniform with the pigment. And a second layer region in which the binder is crosslinked by the second crosslinking agent so that the degree of crosslinking is larger than that of the first layer region, and the first layer region is more than the second layer region. It is possible to effectively form the ink receiving layer located on the ink recording surface side.

Furthermore, the first and second surface treatments with the second cross-linking agent can be performed on the substrate stepwise. Coating solution used in the surface treatment step, for the reasons mentioned above, for example, preferably so as to be 0.05 g / m ² or more 2.0 g / m ² or less of the dry coating amount in terms of solid content. In the first surface treatment step, for example, when the binder is polyvinyl alcohol, for example, a coating liquid containing one or more selected from the group consisting of boric acid and borate, for example, 5% by mass of borax The aqueous solution is applied onto the undercoat layer of the substrate and then dried and solidified. You may make the said coating liquid contain solvents, such as alcohol, for a defoaming as needed. Since it is preferable to reduce the amount of dry coating in the first surface treatment step, the coating and drying speed can be considerably increased. For example, high-speed processing at 50 to 200 m per minute is possible. .

  In the second surface treatment step performed after the first surface treatment step described above, the surface treatment-treated substrate subjected to the first surface treatment step is further applied in the same manner as in the case of the first surface treatment. When the binder is polyvinyl alcohol, for example, a coating solution containing at least one selected from the group consisting of boric acid and borate is applied. In the second surface treatment, unlike the case of the first surface treatment step, the coating liquid is not dried and solidified after coating. That is, the surface of the substrate forms a certain amount of wet state (coating liquid state or thickened state may be used), and while maintaining this state, the coating liquid for forming the next ink receiving layer is applied. Is done. By doing so, a reaction state at the liquid-liquid interface is ensured between the coating liquid and the second cross-linking agent. That is, at this interface, the gelation rate or the crosslinking rate of the ink receiving layer coating solution is increased.

  The stepwise surface treatment has the following advantages. Since the coating solution is dried in the first surface treatment step performed on the substrate, boric acid or borate (hereinafter referred to as borate, etc.) is formed on the substrate or in the undercoat layer (upper part of the layer). Will exist as a solid. Then, when the next second surface treatment and the formation of the ink receiving layer are performed in this state, boric acid or an aqueous borate solution (hereinafter referred to as a borate treatment liquid or the like) applied in the second surface treatment step. In particular, there is an advantage that the borate treatment liquid or the like can reliably ensure a liquid surface. Therefore, it is also ensured that the ink receiving layer coating liquid in the next step is mixed with the borate treatment liquid and the like coated in the second surface treatment step in a liquid-liquid state.

  By adopting the surface treatment consisting of these two steps, the wet state can be formed more stably with the borate treatment liquid or the like on the surface of the substrate on which a solid such as borate is present. On the undercoat layer in this state, a rapid cross-linking reaction can be obtained at the interface due to the liquid-liquid contact, and pores between the pores formed with a solvent such as water in the coating liquid forming the ink receiving layer Can be removed while being separated from the binder, so that ideal aggregation of the pigment and proper binding due to the presence of the binder can be formed in a uniform state. As a result, the occurrence of cracks due to insufficient binder during production is suppressed, and a thick ink-receiving layer with a large amount of dry coating can be formed.

  The boric acid and borate used in the second surface treatment step can be the same as those used in the formation of the ink receiving layer or in the first surface treatment step. Use borax in terms of gelation speed or crosslinking speed in the receiving layer formation stage, viscosity change of the ink receiving layer coating liquid generated during use, and the effect of suppressing the occurrence of cracks in the formed ink receiving layer. Is preferred. In the second surface treatment step, it is preferable to set the coating amount to such an extent that the coating liquid does not overflow just on the first surface-treated substrate. Depending on the absorbency of the first surface-treated substrate, if there is a lot of overflow of the coating solution for the second surface treatment, the coating solution for the ink-receiving layer is applied when the coating solution for the ink-receiving layer is applied. However, there is a risk of floating due to overflow of the coating liquid used in the second surface treatment, and the adhesiveness of the ink receiving layer to the substrate may be lowered.

Furthermore, in the second surface treatment step, one or more selected from the group consisting of boric acid and borate so as to obtain a dry coating amount of 0.05 to 2.0 g / m ^{2 in} terms of solid content. It is preferable to adjust the solid content concentration. In the second surface treatment step, a coating liquid containing at least one selected from the group consisting of boric acid and borate, for example, a 5% by mass aqueous solution of borax, is used as the first surface treatment. Coat on the finished primer layer. You may make the said coating liquid contain solvents, such as alcohol, for a defoaming as needed.

Furthermore, the dry coating amount of the coating liquid applied in the first and second surface treatment steps can be appropriately determined from the relationship between the first and second surface treatments. For example, when reducing the coating amount in the first surface treatment step, it can be compensated by increasing the coating amount in the second surface treatment step, but it is easy to control the coating amount. In consideration of the relationship with the coating amount in the second surface treatment step to be performed next, the dry coating amount in the first surface treatment step is 0.1 to 1.0 g / m ^2. In consideration of the relationship between the coating speed and the coating amount in the first surface treatment, the dry coating amount of the coating liquid in the second surface treatment step is 0.3 to 1.5 g / m. ² is preferable. The wet surface is not a uniform surface but has a recess for the coating liquid, and by causing cross-linking of the binder in the recess, the adhesion of the ink receiving layer to the substrate and the anchor effect can be ensured. This is a configuration having a crosslinked binder in the concave portion, but is also an effective configuration for the formed recording medium. In the preparation of the ink receiving layer coating liquid, at least one selected from the group consisting of boric acid and borate is mixed with an alumina hydrate dispersion, and the resulting liquid mixture and a binder. It is preferable to use a mixing apparatus in which a polyvinyl alcohol aqueous solution is mixed immediately before coating to form a coating liquid. By doing so, it is possible to reduce the time-dependent increase in the viscosity of the coating solution and the gelation that occur during the production process, so that the production efficiency can be improved. The solid content concentration of the pigment in the alumina hydrate dispersion used above is preferably 10 to 30% by mass. When the above range is exceeded, the viscosity of the pigment dispersion increases and the viscosity of the ink receiving layer also increases, which may cause problems in coating properties.

  In the embodiment relating to the ink receiving layer, as the constitution of the ink receiving layer, since the presence of the binder in the ink receiving layer can be properly positioned with respect to the pigment, it is mainly given by the coating liquid. And the pore distribution formed by the binder can be made uniform. At the same time, a substantial barrier layer region that prevents the binder from being lost to the substrate side from the coating liquid is formed by a high-speed, high-probability reaction state at the liquid-liquid interface between the two coating liquids. Therefore, the degree of crosslinking itself can be increased. Particularly preferably, in order to achieve efficient removal of the solvent in the coating solution, a solvent for dissolving the binder of the coating solution (water in the case of PVA (preferably pure water as a measure against dust against alumina). )) And other liquid components are preferably excluded from the coating liquid during the crosslinking reaction or the like, so that the recording medium for ink is used as a base material for supporting the ink receiving layer. It is preferable to have a porous body (paper, pulp, porous layer, etc.) through which the liquid component can penetrate.

  For the undercoat layer and the above ink-receiving layer, as other additives, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, mold release agents, penetrating agents, colored pigments, coloring Dyes, fluorescent brighteners, ultraviolet absorbers, antioxidants, antiseptics, antifungal agents, water resistance agents, dye fixing agents, and the like can be appropriately contained as necessary.

  The present inventors consider that the formation of the ink receiving layer of the ink recording medium according to the present invention is performed due to the following phenomenon. First, by the action of boric acid or borate used for the surface treatment of the substrate and the polyvinyl alcohol in the ink receiving layer coating solution, that is, gelation and / or crosslinking reaction, (1) undercoating of polyvinyl alcohol The penetration into the layer is suppressed, so that the binder in the ink receiving layer can be distributed relatively uniformly, and further, (2) gelation and / or crosslinking reaction in the drying stage when forming the ink receiving layer It is presumed that this is due to the fact that the movement of the coating liquid can be reduced because the viscosity increases due to the occurrence of water. In particular, when alumina hydrate is used as the material for forming the ink receiving layer, a so-called inorganic polymer is formed by a crosslinking reaction between the alumina hydrate and boric acid or borate. It is speculated that the interaction between alumina hydrate and polyvinyl alcohol works to suppress cracks in the ink receiving layer.

  The substrate used in the present invention is not particularly limited as long as the surface treatment described below can be performed. However, when a glossy surface is formed by performing a casting process on the surface of the recording medium for ink, water or Since the solvent component evaporates from the back surface of the substrate, a fibrous substrate, that is, a paper substrate is preferable. Paper base materials include those that have been subjected to size press with starch, polyvinyl alcohol, etc. on the base paper, and coated papers such as art paper, coated paper, cast coated paper, etc. that have a coating layer on the base paper It is.

When paper is used as the base material when a casting process is performed on the surface of the ink recording medium to form a glossy surface, the cellulose pulp fibers and texture of the paper base material (base paper) are completely covered. A coat layer having a thickness is preferably provided as an undercoat layer of the ink receiving layer. If it is not covered, uneven coating (such as streak-like defects) is likely to occur due to the fibers and texture when the ink receiving layer is applied. Cellulose pulp fibers in the ink receiving layer or near or on the surface of the ink receiving layer Therefore, even when the surface of the ink recording medium is cast, it may be difficult to obtain a good and homogeneous cast surface, that is, a photographic high gloss surface. is there. In order to cover the cellulose pulp of the paper substrate, the dry coating amount of the coating layer is preferably 10 g / m ² or more, more preferably 15 g / m ² or more. When the dry coating amount is less than 10 g / m ² , it is difficult to completely cover the cellulose pulp fibers and the texture of the base material, which may affect the gloss.

  The undercoat layer can be formed by a conventionally known coating solution containing a pigment and a binder, but preferably has ink acceptability. One or more undercoat layers can be provided on at least one surface of the substrate. Considering the stability of the environmental curl of the ink recording medium, the undercoat layer is preferably provided on both the front and back surfaces of the substrate. The base material used in the present invention includes a paper base material provided with the undercoat layer. Evaporation of water and solvent components from the back of the substrate in the casting process, coating properties (wetting properties) of the coating liquid to be applied to the substrate in the first and second surface treatment steps described below, In consideration of the coating property of the ink-receiving layer forming material formed thereon, it is preferable that the air permeability (JIS P 8117) of the base material is 1,500 to 5,000 seconds. When the air permeability is less than the above range, since the denseness of the base material is low, the crosslinking agent (boric acid or borate in the coating liquid) in the first and second surface treatment steps described below. There are cases where the penetration is high and not all of the cross-linking agents work effectively. Alternatively, a larger application amount is required. Also, in the second surface treatment step, it is preferable that the coating state penetrates without overflowing, but it is difficult to adjust the coating amount, and stable coating over time in the entire CD / MD direction is difficult. It becomes.

On the other hand, when the air permeability of the substrate exceeds the above range, the permeability of the coating liquid to be applied in the first and second surface treatment steps described later is low, and the coating liquid for the ink receiving layer is further added thereto. When the ink receiving layer is applied, the ink receiving layer coating liquid may float due to overflow of the coating liquid used for the second surface treatment, or a slight crack may be formed in the formed ink receiving layer. Furthermore, during casting, water and solvent components from the back surface of the substrate are less likely to evaporate, and a good glossy surface may not be obtained. For the same reason, it is preferable that the base material has a Steecht size of 100 to 400 seconds and a Beck smoothness of 100 to 500 seconds. In addition, in order to obtain a recording medium having the same texture and high quality as a silver salt photograph, the basis weight of the base material is 160 to 230 g / m ² , and the Gurley stiffness (J. Tappi No. 40, vertical mesh) is 7 to It is preferable to be 15 mN.

  The material for forming the ink receiving layer used in the present invention will be described. The ink receiving layer can be formed by applying a coating liquid containing a pigment and a binder. As the pigment, it is particularly preferable to contain alumina hydrate as a main component in terms of dye fixing property, transparency, printing density, color developability, and glossiness, but the following pigments can also be used. Examples of inorganic pigments include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, magnesium hydroxide, and other organic pigments. Examples thereof include styrene plastic pigments, acrylic plastic pigments, polyethylene particles, microcapsule particles, urea resin particles, and melamine resin particles. One kind selected from these, or two or more kinds selected as necessary can be used in combination.

As the alumina hydrate, for example, one represented by the following general formula (1) can be suitably used.
_{Al 2 O 3 -n (OH)} 2n · mH 2 O ··· (1)
(In the above formula, n represents any of 0, 1, 2, or 3, and m represents a value in the range of 0 to 10, preferably 0 to 5. However, m and n are not 0 at the same time. MH ₂ O often represents a detachable aqueous phase that does not participate in the formation of the crystal lattice, so m can be an integer or non-integer value. M can reach a value of 0 when heated.)
Alumina hydrate is generally produced by hydrolysis of aluminum alkoxide or sodium aluminate as described in US Pat. Nos. 4,242,271 and 4,202,870. Known methods such as a method for performing decomposition, and a method for performing neutralization by adding an aqueous solution such as aluminum sulfate and aluminum chloride to an aqueous solution such as sodium aluminate described in JP-B-57-447605 Can be manufactured. Preferred alumina hydrates in the present invention are alumina hydrates showing a boehmite structure or an amorphous state by analysis by X-ray diffraction, and in particular, JP-A-7-232473 and JP-A-8-132731. And alumina hydrates described in JP-A-9-66664, JP-A-9-76628, and the like.

  In order to impart gloss to the surface of the ink recording medium, it is preferable to use a plate-like alumina hydrate having a low tendency to be oriented when the ink receiving layer is wetted by the rewetting method and the casting process is performed. . Since the plate-like alumina hydrate has a good water absorbability, the re-wetting liquid easily penetrates, so that the ink receiving layer swells and the alumina hydrate particles are easily rearranged. Therefore, high glossiness can be obtained. Moreover, since the rewetting liquid penetrates efficiently, the production efficiency at the time of casting is also increased.

  In the present invention, polyvinyl alcohol is used as the binder used in the coating liquid for forming the ink receiving layer. The content of polyvinyl alcohol is preferably 5 to 20% by mass with respect to the alumina hydrate. In the present invention, as the binder used in forming the ink receiving layer, a conventionally known binder can be used in combination with the above-described polyvinyl alcohol.

Including at least one selected from the group consisting of boric acid and borate in the ink receiving layer forming material formed as described above is extremely effective in forming the ink receiving layer. Examples of boric acid that can be used in this case include not only orthoboric acid (H3BO3) but also metaboric acid and hypoboric acid. The borate is preferably a water-soluble salt of boric acid. Specifically, for example, sodium salt of boric acid (Na ₂ B ₄ O ₇ · 10H ₂ O, NaBO ₂ · 4H ₂ O etc.) and, potassium salt _{(K 2 B 4 O 7 ·} 5H 2 O, alkali metal salts such KBO _2, etc.), an ammonium salt of boric acid _{(NH 4 B 4 O 9 ·} 3H 2 O, NH 4 BO 2 , etc. ), Alkaline earth metal salts such as magnesium salts and calcium salts of boric acid.

  It is preferable to use orthoboric acid from the viewpoint of the temporal stability of the coating solution and the effect of suppressing the occurrence of cracks. Further, the amount used is preferably in the range of 1.0 to 15.0% by mass of boric acid solid content with respect to polyvinyl alcohol in the ink receiving layer. Even within this range, cracks may occur depending on manufacturing conditions and the like, and selection is required. On the other hand, exceeding the above range is not preferable because the temporal stability of the coating solution is lowered. That is, in the case of production, since the coating liquid is used for a long time, if the content of boric acid is large, the viscosity of the coating liquid increases during that time, and the generation of a gelled product occurs. It is necessary to frequently change the coating liquid and clean the coater head, and the productivity is significantly reduced. Furthermore, when the above range is exceeded, for the same reason as the first and second surface treatments described later, in the casting step, a point-like surface (cast surface) defect is likely to occur, and a uniform and good glossy surface is obtained. There may not be.

The ink receiving layer formed as described above preferably has the pore properties satisfying the following conditions in order to achieve the purpose and effect such as high ink absorbability and high fixability. First, the pore volume of the ink receiving layer is preferably in the range of 0.1 to 1.0 cm ³ / g. That is, when the pore volume is less than the above range, sufficient ink absorption performance cannot be obtained, resulting in an ink receiving layer with poor ink absorption, and in some cases, ink overflows and bleeding occurs in the image. There is a fear. On the other hand, when it exceeds the above range, there is a tendency that cracks and powder fall off easily occur in the ink receiving layer. The BET specific surface area of the ink receiving layer is preferably ^{20 to} 450 m ² / g. If it is less than the above range, sufficient gloss may not be obtained, and haze increases (transparency decreases), so the image appears to be “white haze”. There is a fear. Furthermore, this case is not preferable because there is a possibility that the adsorptivity of the dye in the ink may be lowered. On the other hand, exceeding the above range is not preferable because cracks are likely to occur in the ink receiving layer. The values of the pore volume and the BET specific surface area are obtained by a nitrogen adsorption / desorption method.

Further, when forming the ink receiving layer, by using the production method of the present invention, the thickness of the ink receiving layer is increased as compared with the prior art, that is, it can be made thicker than before. In consideration of high ink absorbability, the dry coating amount is preferably at least 30 g / m ² , and the upper limit is more preferably 50 g / m ² . If it is less than 30 g / m ² , the ink absorption is sufficient especially when used in a printer in which a plurality of light-color inks are added in addition to black ink in addition to the three colors of cyan, magenta, and yellow. In other words, ink overflow may occur and bleeding may occur, or ink dye may diffuse to the base material and print density may decrease. On the other hand, when it exceeds 50 g / m ² , it may occur that the generation of cracks cannot be completely suppressed. Furthermore, if it is 30 g / m ² or more, an ink receiving layer exhibiting sufficient ink absorbency even in a high temperature and high humidity environment can be obtained, and if the dry coating amount is 50 g / m ² or less, ink receiving is possible. The coating unevenness of the layer is further less likely to occur, and an ink receiving layer having a stable thickness can be produced.

In forming the ink receiving layer, a method of applying and drying once, a method of obtaining a desired dry coating amount as a whole by applying a plurality of times, and the like can be used. For example, in the case of two coats, the dry coating amount of 20 g / m ² formed by the first round of the coating and drying process, the remaining 20 g / m ² in Part 2 of the coating and drying process It is possible to obtain an ink receiving layer having a dry coating amount of 40 g / m ² . In addition, even in such an ink receiving layer formed by multiple times of application, by applying the method for applying the coloring material deterioration preventing material of the present invention to the ink receiving layer, the depth direction intended in the present invention The concentration distribution of the color material deterioration preventing material can be obtained.

  As the boric acid and borate contained in the coating liquid used in the first and second surface treatment steps of the present invention, those similar to those used as the ink receiving layer forming material are used. In particular, sodium tetraborate (borax) is preferably contained from the viewpoint of the effect of suppressing the occurrence of cracks.

  In order to obtain an appropriate coating amount as described above, for example, various blade coaters, roll coaters, air knife coaters, and bar coaters are applied to the ink receiving layer and the surface treatment process described above. , Rod blade coater, curtain coater, gravure coater, coater using extrusion method, coater using slide hopper method, size press etc. Is done. At the time of coating, for the purpose of adjusting the viscosity of the coating solution, the coating solution may be heated, or the coater head can be heated.

  For drying after coating, for example, a straight tunnel dryer, an arch dryer, an air loop dryer, a hot air dryer such as a sine curve air float dryer, a dryer using infrared rays, a heated dryer, a microwave, etc., as appropriate. It can be selected and used.

  Next, an embodiment relating to the external addition method of the colorant deterioration preventing material will be described.

  Hereinafter, the color material deterioration preventing material according to the present invention will be described. The colorant deterioration preventing material in the present invention refers to a compound that protects the dye from factors that degrade the dye, such as gas and light, and improves the weather resistance of the dye when present together with the dye in the ink receiving layer. General examples include hindered amine compounds, hindered phenol compounds, benzophenone compounds, benzotriazole compounds, thiourea compounds, thiuram compounds, phosphite compounds, etc. It is not limited to. Among the colorant deterioration preventing materials, hindered amine compounds are particularly preferable from the viewpoints of light resistance, moisture resistance, water resistance and the like. As the hindered amine compound, a compound having at least one hindered amine structure represented by the following formula (1) in the molecule is preferable.

Here, R ^{1 to} R ⁴ are each independently a lower alkyl group having 1 to 5 carbon atoms, particularly preferably a methyl group or an ethyl group. R ⁵ is not particularly limited, and is a hydrogen atom, a lower alkyl group, a benzyl group, an allyl group, an acetyl group, an alkoxyl group, a benzyloxy group, or the like. A is not particularly limited, and is an alkyl group, an alkoxyl group, an amino group, an amide group, a carboxyl group or the like. A may be, for example, an ester group of dicarboxylic acid such as malonic acid, adipic acid, succinic acid, sebacic acid, maleic acid, phthalic acid or the like, or an ester group of tricarboxylic acid or tetracarboxylic acid, and other hindered amine structures. It may be a group that links Furthermore, A may be a group having a vinyl group such as a (meth) acrylic ester group, and in this case, it may be a polymer having a hindered amine structure in the side chain.

  The organic solvent for dissolving the colorant deterioration preventing material in the present invention is not particularly limited, but esters such as ethyl acetate and butyl acetate, ketones such as methyl isobutyl ketone, methyl ethyl ketone and acetone, diethyl ether, Examples include ethers such as ethyl methyl ether, and alcohols such as isopropanol, methanol, and ethanol. As this solvent, when the coating solution of the color material deterioration preventing material is applied to the ink receiving layer and subsequently subjected to a rapid drying process, it effectively evaporates to prevent the color material deterioration targeted in the present invention. A material capable of obtaining a distribution in the depth direction of the material is appropriately selected. For example, it is good to obtain such an effect in heat treatment at 80 ° C. or higher, preferably 80 ° C. to 180 ° C., and it can be selected in consideration of the type of the color material deterioration preventing material to be used.

  In the present invention, as a method of externally adding the color material deterioration preventing material to the recording medium for ink, the color material deterioration preventing material is a color material deterioration preventing material solution in which at least one kind of organic solvent is dissolved. Then, after completely dissolving, it may be coated on the formed ink receiving layer. The solid content concentration of the color material deterioration preventing material is easily 0.5 to 30% by mass. From the viewpoint of the appearance of the ink recording medium after finishing, the coating method of the colorant deterioration preventing material is preferably a non-contact coating method with respect to the receiving layer surface, and examples include a die coater, an air knife coater, and a spray. However, a contact-type coating method such as a roll coater, bar coater, or gravure coater can also be used.

  In the drying process after coating, it is important to move to the drying process within a short time that the coloring material deterioration preventing material cannot completely penetrate, and it is preferable to move to the drying process within 10 hours after coating. Should be within 5 seconds. Moreover, it is preferable that the time from the start of the drying process to the time when the drying is completed is completed within 1 minute, and more preferably within 30 seconds. The air volume can also be adjusted for efficient drying.

  The preferable content of the colorant deterioration preventing material in the ink receiving layer is preferably in the range of 0.5 to 10 parts by mass with respect to 100 parts by mass of the pigment solid content. By setting it to the above lower limit or more, a sufficient discoloration suppressing effect can be obtained. Further, by setting the amount to be equal to or less than the above upper limit, it is possible to prevent the ink absorbability from being lowered.

  As shown in FIG. 3, the color material deterioration preventing material in the present invention includes two portions having different concentrations of the color material deterioration preventing material in a range from the recording surface side of the ink receiving layer to 30 μm in the depth direction. The recording surface in the depth direction of the ink receiving layer is higher in the higher density portion of the color material deterioration preventing material than in the lower density portion in which the density of the color material deterioration preventing material is lower. It is preferably located on the side. By doing so, the effect of the colorant deterioration preventing material can be sufficiently exhibited.

  More preferably, the color material deterioration preventing material preferably has a density distribution that gradually decreases from the recording surface side of the ink receiving layer. By doing so, since the color material deterioration preventing material is present along the penetration of the dye, the effect can be further exhibited. It is preferable that the density distribution of the color material deterioration preventing material has a density distribution that decreases from the recording surface to the depth direction, particularly at a position of 15 μm from the recording surface of the ink receiving layer to the depth direction. Furthermore, it has always a concentration distribution in which the concentration of the colorant deterioration preventing material decreases in the depth direction in a 10 μm thick portion arbitrarily selected in the depth direction in the upper region 15 μm deep from this surface. More preferred. For example, in any of the region from the surface to a depth of 10 μm, the region from 3 μm to 13 μm in depth, and the region from 5 μm to 15 μm in depth, there is a concentration distribution in which the concentration of the color material deterioration preventing material decreases in the depth direction. Preferably there is. Further, it has a concentration distribution in which the concentration of the colorant deterioration preventing material is always decreased in the depth direction in the 5 μm thick portion arbitrarily selected in the depth direction in the upper region 15 μm deep from the surface. preferable. For example, the concentration distribution in which the concentration of the colorant deterioration preventing material decreases in the depth direction in any of the region from the surface to a depth of 5 μm, the region from 3 μm to 8 μm in depth, and the region from 10 μm to 15 μm in depth. More preferably it is.

  Note that the concentration reduction rate in the arbitrarily selected region is selected to be larger than the reduction rate in a similar depth range in a region having a depth exceeding 15 μm. Further, the reduction here may be stepwise or continuous.

  On the other hand, it is desirable that the density of the highest density portion of the color material deterioration preventing material is 1.5 times or more the density of the lowest density portion. If the density difference is 1.5 times or less, the proportion of the color material deterioration preventing material that does not exhibit the effect increases, and the desired effect cannot be obtained. Further, it is more preferable that this density difference exists at a position from the recording surface of the ink receiving layer to 15 μm in the depth direction.

  After forming the ink receiving layer as described above, a glossy surface can be formed on the surface of the ink receiving layer by a casting method. The manufacturing method will be described. The casting method is a method in which an ink receiving layer in a wet state or a plastic state is pressure-bonded to a heated mirror-like drum (cast drum) surface, dried in the pressure-bonded state, and the mirror surface is ink-coated. This is a method of copying on the surface of the receiving layer, and there are three typical methods, namely, a direct method, a rewet method (indirect method), and a coagulation method. Any of these casting methods can be used. However, as described above, in the present invention, it is preferable to use alumina hydrate in the ink receiving layer of the ink recording medium. In particular, the use of the rewet cast method is more preferable because high gloss can be obtained.

  In the method for producing a recording medium for ink according to the present invention, a back layer forming step is further added to the back surface of the base material (the surface opposite to the side on which the ink receiving layer is formed), and the ink substrate having the back surface layer is added. A recording medium may be manufactured. The formation of the back layer is effective for reducing curling that occurs before and after printing.

  In consideration of the curling suppression effect, it is preferable to cause the same shrinkage as the undercoat layer and / or ink receiving layer on the substrate surface side at the time of moisture absorption, and it is preferable to use the same type of pigment or binder as those layers. . In particular, it is more preferable to use a pigment or binder of the same type as the material for forming the ink-receiving layer which is a thicker layer. The back surface layer can be formed before, after the first surface treatment, after the ink receiving layer is formed, or after the casting step.

  Furthermore, when the ink recording medium according to the present invention is manufactured, another layer such as the above-described undercoat layer may be provided between the back surface layer and the base material, if necessary. In this case, it is possible to form a glossy surface on the back side, and an ink recording medium having glossy surfaces on both the front and back sides can be obtained. In addition, double-sided printing is possible by providing printing performance to the back surface layer, or the back surface layer and / or another layer.

  Further, when the back layer is provided, the first surface treatment / second surface treatment / back surface layer formation, that is, the first surface treatment is performed on the back surface of the base material in order to suppress cracks as in the case of the ink receiving layer. Thereafter, a second surface treatment may be performed, and the back layer coating solution may be applied and dried while the substrate is maintained in a wet state. However, in some cases (that is, depending on the state of occurrence of cracks in the back surface layer), only one of the first and second surface treatments may be required. The configuration of the ink recording medium manufactured as described above is shown in a schematic cross-sectional view as shown in FIG. 7 as a preferred example. That is, by base paper 1 as a base material, undercoat layer 2 containing pigment, binder, etc., undercoat layer 3, coating of borax-containing coating liquid, surface treatment part 4 by drying, coating of borax-containing coating liquid Surface treatment section 5, ink receiving layer 6 (containing alumina hydrate, polyvinyl alcohol, boric acid, etc.) formed by coating and drying while the undercoat layer / base paper is kept wet by this surface treatment, It is the structure of the back surface layer 7 containing a pigment, a binder or the like.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited to these examples.

First, measurement methods and evaluation methods for various physical property values used in the present invention will be described.
<Stick human sizing degree>
The sample was cut to A4 size, and the 5 sheets were left to stand for 2 hours or more under the conditions of an air temperature of 23 ° C. and a humidity of 50%. Measurement was performed and the average value of 5 sheets was obtained.
<Air permeability>
After leaving the sample in the same state as in the measurement of the above-mentioned Steecht sizing, each sample was measured according to JIS P8177, and the average value of five values was obtained.
<Beck smoothness>
After the sample was left in the same state as in the measurement of the above-mentioned Steecht sizing, each sample was measured according to JIS P8119, and the average value of five values was obtained.
<Gurley stiffness>
After leaving the sample in the same state as in the above-mentioned measurement of the Steecht sizing degree, the longitudinal direction is measured for each piece according to J. Tappi No. 40, and the average value of the five pieces is obtained. Asked.
<BET specific surface area, pore volume>
The alumina hydrate was sufficiently degassed by heating, and then measured with an apparatus using a nitrogen adsorption / desorption method (manufactured by Cantachrome, Autosorb 1). The BET specific surface area was calculated using the method of Brunauer et al. (See J. Am. Chem. Soc., 60, 309, 1938). The pore volume was calculated using the method of Barrett et al. (See J. Am. Chem. Soc., 73, 373, 1951).

<Glossiness>
According to JIS Z8741, a specular gloss of 20 degrees was measured using a gloss meter (trade name: VG2000, manufactured by Nippon Denshoku Industries Co., Ltd.).
<Image robustness>
Creation of recorded material: Using a photo printer (product name: PIXUS 950i Canon) using an inkjet method, a 100% Duty solid batch of black, cyan, magenta, and yellow was printed on the recording surface of each recording medium. It was decided to print and use for the test.
<Ozone test>
The evaluation method of ozone resistance is to measure the image density of the recorded matter before and after the test using a spectrophotometer and spectrino (manufactured by Gretag Macbeth). The rate was determined.
Density residual ratio (%) = image density after test / image density before test × 100
The ozone resistance evaluation was determined based on the criteria described below, and the results are shown in Table 1. The image created above was subjected to a gas exposure resistance test using an ozone exposure tester (manufactured by Suga Test Instruments Co., Ltd.).
・ Test condition ozone concentration: 2.0ppm
Test time: 1.5 hours Temperature and humidity conditions in the test layer: 23 ° C., 60% RH,
The gas resistance was evaluated according to the following criteria by the image density remaining rate (%) after the ozone exposure test and visual judgment.
4: Bk density residual rate is 80% or more, and other color density residual rate is 90% or more.
3: Bk density remaining rate is 70% or more and less than 80%, or other color density remaining rate is 80% or more and less than 90%, and the color tone is slightly changed compared to before the test. (Except for 1 and 2 standards)
2: The Bk density remaining rate is less than 70% or other color density remaining rate is 70% or more and less than 80%. (Except for standard 1)
1: BK concentration remaining rate is less than 70%, or other concentration remaining rate is less than 70%, and clearly has a different color than before the test.
<The second ozone test>
After the ozone test is completed, the same ozone test is performed again using the same sample.

The determination was made based on the above criteria, and the results are shown in Table 1.
<Ink absorbability>
Using BJF900 (manufactured by Canon Inc.), 100% printed areas of 3 cm squares of yellow, magenta, cyan, and black that are single colors, and red that is a secondary color (secondary colors of yellow 100% and magenta 100%) Blue (secondary color of 100% of magenta and 100% of cyan) and green (secondary color of 100% of yellow and 100% of cyan) were printed on each 100 cm printed portion of 3 cm square. Then, a four-stage evaluation was performed by visual observation of the printed part and a finger. The evaluation criteria are as follows.
4: Immediately after printing, ink does not adhere to the finger in all of the secondary color images.
3: Immediately after printing, there is a slight ink overflow in the secondary color image, but it is absorbed in a short time, and ink does not adhere to the finger in all the single color images immediately after printing.
2: Immediately after printing, there is a slight ink overflow in the secondary color image, and although it takes more time than in the case of evaluation 3, it is absorbed and ink does not adhere to the finger in all of the single color images immediately after printing.
1: Immediately after printing, ink adheres to the finger in one of the monochrome images.

[Example 1]
First, the base material was produced as follows. Cationized starch 0.60 was added to a pulp slurry comprising 80 parts by mass of hardwood bleached kraft pulp (LBKP) having a freeness of 450 ml CSF (Canadian Standarad Freeness) and 20 parts by mass of softwood bleached kraft pulp (NBKP) having a freeness of 480 ml CSF. After adding parts by weight, 10 parts by weight of heavy calcium carbonate, 15 parts by weight of light calcium carbonate, 0.10 parts by weight of alkyl ketene dimer and 0.03 parts by weight of cationic polyacrylamide, the stock is adjusted, and then the long net papermaking The paper was made by a machine, subjected to a three-stage wet press, and dried with a multi-cylinder dryer. After that, impregnated with an oxidized starch aqueous solution to a solid content of 1.0 g / m ² with a size press machine, dried and machine calendered, basis weight 155 g / m ² , Steecht size 100 seconds, A base material having an air permeability of 50 seconds, a Beck smoothness of 30 seconds, and a Gurley stiffness of 11.0 mN was obtained.

Next, an undercoat layer was formed on the substrate obtained above as follows. First, as a coating liquid used for forming the undercoat layer, 100 parts by mass of kaolin (Ultra White 90, manufactured by Engelhard) / zinc oxide / aluminum hydroxide having a weight ratio of 65/10/25, and commercially available 7 parts by mass of a commercially available styrene-butadiene latex was added to a slurry having a solid content of 70% by mass comprising 0.1 part by mass of a polyacrylic acid-based dispersant and adjusted so as to have a solid content of 60% by mass. To obtain a composition. Next, this composition was coated on both sides of the substrate with a blade coater so that the dry coating amount was 15 g / m ² and dried. After that, machine calender finishing (linear pressure 150 kgf / cm), basis weight 185 g / m ² , Steecht size degree 300 seconds, air permeability 3,000 seconds, Beck smoothness 200 seconds, Gurley stiffness 11.5 mN undercoat A layered substrate was obtained. The whiteness of the base material with the undercoat layer was measured for each of the five A4 size samples cut and obtained as an average value. As a result, L *: 95, a *: 0, b *: -2 (determined as the hue of JIS Z 8729).

The undercoat layer obtained above was subjected to surface treatment comprising the following first and second steps. First, in the first surface treatment step, a 5% by mass borax aqueous solution heated to 30 ° C. was used as a coating solution, and the coating solution was dried with a gravure coater in an amount of 0.4 g / m ^2. Was applied onto the undercoat layer at a rate of 60 m / m / min. And the coating liquid was dried and solidified at 60 degreeC. Next, in the second surface treatment step, a 5% by mass borax aqueous solution heated to 30 ° C. similar to that used in the first surface treatment step is used, and the coating solution is applied with an air knife coater. The coating was performed at 30 m / min so that the wet coating amount was 10 g / m ² (the coating amount when dried was 0.5 g / m ² ). When this amount of coating was observed with the naked eye, the coating solution applied in the second surface treatment step did not overflow on the undercoat layer and was just impregnated.

  Next, an ink receiving layer was formed. After coating in the second surface treatment step, that is, as soon as the coating solution was impregnated in the undercoat layer, the ink receiving layer was formed on the undercoat layer as it was. did. The coating liquid and coating method used for forming the ink receiving layer at that time are as follows.

Dispersal HP13 (manufactured by Sasol Co.) as alumina hydrate A was dispersed in water (preferably pure water as a measure against dust for alumina) so that the solid content was 5% by mass, and then hydrochloric acid was added thereto. The pH value was adjusted to 4 and stirred for a while. Thereafter, the dispersion was heated to 95 ° C. while stirring and held at that temperature for 4 hours. Then, while maintaining this temperature, the pH value was adjusted to 10 with caustic soda and stirred for 10 hours, and then the temperature of the dispersion was returned to room temperature and the pH value was adjusted to 7-8. Further, desalting treatment was performed, and then acetic acid was added to peptize to obtain a colloidal sol. Further, when alumina hydrate B obtained by drying the colloidal sol was measured by X-ray diffraction, it showed a boehmite structure (pseudo boehmite). At this time, the BET specific surface area was 143 g / m ² , the pore volume was 0.8 cm ³ / g, and it was flat when observed with an electron microscope.

On the other hand, polyvinyl alcohol JM-23 (manufactured by Nippon Vinegar Bipovar Co., Ltd.) was dissolved in water (preferably pure water as a measure against dust against alumina) to obtain an aqueous solution having a solid content of 9% by mass. Then, the colloidal sol of alumina hydrate B prepared above is concentrated to prepare a 22.5 mass% dispersion, and 3 mass% boric acid aqueous solution is added to the solid content of alumina hydrate B. Was added so as to be 0.50% by mass in terms of solid content of boric acid. Thereafter, the obtained boric acid-containing alumina hydrate dispersion and the previously prepared polyvinyl alcohol aqueous solution were mixed with an alumina hydrate solid content and a polyvinyl alcohol solid content ratio of 100: 8 using a static mixer. Immediately after mixing, this was used as a coating solution for the ink receiving layer, and this was coated with a die coater at 30 m / min so that the dry coating amount was 35 g / m ² . And it dried at 170 degreeC and formed the ink receiving layer.

Next, a back surface layer was formed as follows on the undercoat layer on the surface opposite to the surface on which the ink receiving layer of the base material was provided. Dispersal HP13 / 2 (manufactured by Sasol Co., Ltd.) as an alumina hydrate is dispersed in water (preferably pure water as an anti-dust measure against alumina) so that the solid content is 18% by mass, and then centrifuged. did. Immediately after mixing this dispersion and an aqueous polyvinyl alcohol solution similar to that used for forming the ink receiving layer with a static mixer so that the ratio of solids of alumina hydrate to polyvinyl alcohol was 100: 9, The coating was performed at 35 m / min so that the dry coating amount was 23 g / m ² with a die coater. And it dried at 170 degreeC and formed the back layer.

The difference in the degree of crosslinking between the first layer region and the second layer region was estimated from the amount of boron “B” contained in each layer. Here, the amount of boron “B” contained in the first layer region is calculated as the amount of boron contained in the coating liquid used for forming the ink receiving layer, and boron “B” in the second layer region is calculated. This amount was calculated by assuming that boron penetrates into the second layer region, that is, the dry coating amount of the second surface treatment. The amount of boron “B” contained in the first layer region is 2.61 × 10 ⁻³ mol / m ² , and the second layer region is 9.94 × 10 ⁻³ mol / m ² . The amount of boron “B” contained in the second layer region is 3.8 times the amount of boron “B” contained in the first layer region. The amount of boron “B” contained in the first layer region was calculated from the following equation.
(Ink receiving layer dry coating amount: 35) × (boric acid amount: 22.5 × 0.5%) / {(boric acid amount: 22.5 × 0.5%) + (PVA amount: 22.5) × 8/100) + (alumina hydrate amount: 22.5)} = 0.16 g / m ²
0.16 / (Boric acid 1 mol molecular weight: 61.8) = 2.61 × 10 −3 mol / m ²
The amount of boron “B” contained in the second layer region was calculated from the following equation.
{(Dry coating amount of second surface treatment: 0.5) / (1 mol of borax molecular weight: 201.2)} × (number of moles of B per mol of borax: 4) = 9.94 × 10 ^-3 mol / m ²
Here, the molecular weight of 1 mol of borax was calculated as Na ₂ B ₄ O ₇ because borax was not impregnated into the undercoat layer, that is, not dried.

Next, a 5% by weight MIBK (methyl isobutyl ketone) solution of hindered amine compound ADK STAB LA-63P (Asahi Denka Kogyo Co., Ltd.) is applied to the provided ink receiving layer with a roll coater, and the excess is scraped off with a Mayer bar. The coating was performed at 60 m / min so that the amount was 1.3 g / m ^2, that is, 4% by mass based on the pigment solid content. Then, it was dried at 110 ° C. for 20 seconds within 5 seconds after coating to obtain a target ink recording medium.

  The concentration distribution of the hindered amine in the obtained ink recording medium was measured using the following method. A cross section of a recording medium for ink was prepared using a microtome and subjected to measurement.

The line analysis of the FT-IR microscopic transmission measurement was performed under the following conditions.
Measuring device: Spectrum One (manufactured by perkin-elmer)
Aperture diameter: 98 × 14μm square line Analysis conditions: 120scan / 1step; 1μm / 1step
Measurement wavelength: 1730 cm-1 (IR was measured before and after hindered amine addition, and hindered amine-derived absorption not observed before external addition. See FIG. 8)
FIG. 9 shows the absorbance change of the obtained hindered amine compound in the depth direction of the ink receiving layer. Since the aperture diameter of the measuring apparatus is 14 μm, the measurement was performed with a width of 14 μm from the depth of 7 μm on the first recording surface side, and shifted to the depth of 28 μm by shifting in the depth direction by 1 μm. It was found that the absorbance at that time decreased with increasing depth. The change in absorbance was continuously changing to a depth of 15 μm, and the absorbance change at a position deeper than 15 μm was almost the same quantitative range. Therefore, by having a concentration distribution within the range up to 15 μm, it is possible to increase the absorption efficiency and further improve the effect of the colorant deterioration preventing material. Furthermore, if there is a concentration distribution within the thickness range of 10 μm in the depth direction, a steep distribution can be formed, so that the absorption efficiency and the distribution of the colorant deterioration preventing material can be made ideal, Furthermore, if the condition of the density distribution is premised within the range of 15 μm as viewed from the recording surface, it becomes even better. If the concentration distribution is in the thickness range of 5 μm in the depth direction, the ideal state is obtained. The maximum absorbance was about 1.8 times the minimum absorbance. Therefore, it was found that the highest concentration site of hindered amine was about 1.8 times the lowest concentration site. Thus, it was found that the hindered amine compound has a concentration distribution.

[Example 2]
A recording medium for ink of this example was obtained in the same manner as in Example 1 except that the hindered amine compound was replaced with a thiourea compound Noxeller EUR (Ouchi Shinsei Chemical). Moreover, it was confirmed that the thiourea compound had the same concentration distribution as in Example 1 by IR measurement as in Example 1.
[Example 3]
A recording medium for ink of this example was obtained in the same manner as in Example 1 except that the hindered amine compound was replaced with the hindered phenol compound Sumilizer MDP-9 (Sumitomo Chemical). Moreover, it was confirmed that the hindered phenol compound had the same concentration distribution as in Example 1 by IR measurement as in Example 1.
In addition, the coloring material deterioration preventing material used in Examples 1 to 3 has the following structure.

[Example 4]
An ink recording medium of this example was obtained in the same manner as in Example 1 except that the amount of hindered amine compound added was changed to 0.5% by mass based on the pigment solid content. Moreover, it was confirmed that the hindered amine compound had the same concentration distribution as in Example 1 by IR measurement as in Example 1.
[Example 5]
It was prepared in the same manner as in Example 1 except that the amount of the hindered amine compound added was changed to 10% by mass with respect to the solid content of the pigment, and an ink recording medium of this example was obtained. Moreover, it was confirmed that the hindered amine compound had the same concentration distribution as in Example 1 by IR measurement as in Example 1.
[Example 6]
A glossy surface was formed on the surface of the ink receiving layer of Example 1 by the rewet cast method as follows. First, water as a re-wetting liquid is uniformly applied to the original fabric to wet the ink receiving layer, and in this wet state, it is pressure-bonded to a cast drum having a mirror surface heated to 100 ° C. and dried at 30 m / min. The ink recording medium of this example was obtained. The surface glossiness of the ink receiving layer was 32%. Moreover, it was confirmed that the hindered amine compound had the same concentration distribution as in Example 1 by IR measurement as in Example 1.

[Example 7]
The ink recording medium of this example was obtained in the same manner as the ink recording medium prepared in Example 3, except that the order of the hindered amine external addition step and the casting step was reversed. The surface glossiness of the ink receiving layer was 29%. Moreover, it was confirmed that the hindered amine compound had the same concentration distribution as in Example 1 by IR measurement as in Example 1.

[Example 8]
The recording medium of this example was the same as in Example 1 except that the silica-containing ink receiving layer was formed as follows instead of the alumina hydrate-containing ink receiving layer formed in Example 1. Got. The composition used in the coating liquid for the ink receiving layer includes 100 parts by weight of cationic colloidal silica (trade name: Snowtex AK-ZL, manufactured by Nissan Chemical Industries, Ltd.) having an average particle diameter of 80 nm, and commercially available nonionic properties. A material comprising 3 parts by mass of an acrylic emulsion and 7 parts by mass of polyvinyl alcohol similar to that used in Example 1 was used. This composition was adjusted so that the solid content concentration was 25% by mass, applied with a roll coater so that the dry coating amount was 30 g / m ^2, and then dried. Other steps were performed in the same manner as in Example 1 to obtain a recording medium of this example. Moreover, it was confirmed that the hindered amine compound had the same concentration distribution as in Example 1 by IR measurement as in Example 1.

[Example 9]
Similar to Example 1 except that the first surface treatment step of Example 1 is not performed and the amount of the borax aqueous solution used in the second surface treatment step is changed to 5.2 g / m ² in terms of wet coating amount. Thus, a recording medium was obtained. That is, the amount of boron “B” used in the second surface treatment process of the recording medium is 5.22 × 10 −3 mol / m 2. Moreover, it was confirmed that the hindered amine compound had the same concentration distribution as in Example 1 by IR measurement as in Example 1. The concentration distribution showed that the highest concentration site was 1.49 times the lowest concentration site.
[Example 10]
An ink recording medium was obtained in the same manner as in Example 1 except that both the first and second surface treatment steps of Example 1 were not performed. Moreover, it was confirmed that the hindered amine compound has a concentration distribution by IR measurement as in Example 1. The concentration distribution was found to be 1.40 times higher at the highest concentration site than at the lowest concentration site.

[Comparative Example 1]
A recording medium for ink was obtained in the same manner as in Example 1 except that the hindered amine compound of Example 1 was not externally added.
[Comparative Example 2]
For both the first and second surface treatment steps of Example 1 except that the drying step after applying the colorant deterioration preventing material was omitted and natural drying was performed, as in Example 1 A recording medium was obtained. Further, IR measurement was conducted in the same manner as in Example 1. As a result, a quantitative absorbance of approximately 0.05 was observed in the entire thickness direction, and it was found that the externally added hindered amine compound was uniformly dispersed.

[Comparative Example 3]
The same applies except that the external addition method of the hindered amine compound of Example 1 is changed from the method of adding an organic solvent to the method of mixing the hindered amine compound acid treatment liquid as shown below with the coating liquid used for forming the ink receiving layer. The recording medium for ink was obtained.

  First, using hindered amine compound LA-63P (Asahi Denka) with 1.05 equivalents of acid to the amount of base, the hindered amine compound acid treatment solution was adjusted so that the amount of hindered amine was 35% by mass. did. Next, the external addition method of the hindered amine compound of Example 1 is the same except that the above-described hindered amine compound acid treatment liquid is changed to a method of mixing the coating liquid used for forming the ink receiving layer from the top of the organic solvent. The recording medium for ink was obtained. The hindered amine compound acid treatment solution was mixed and stirred in the coating solution used for forming the ink receiving layer so that the hindered amine compound solid content was 4% by mass with respect to the alumina hydrate solid content. Adjusted.

When IR measurement was conducted in the same manner as in Example 1, it was found that the hindered amine compound was uniformly dispersed in the ink receiving layer without having a concentration distribution.
[Comparative Example 4]
In Comparative Example 3, the same procedure was followed except that the hindered amine acid treatment solution was changed to LX-332 (Asahi Denka) hindered amine emulsion to obtain a recording medium for ink. Further, IR measurement similar to that in Example 1 revealed that the hindered amine compound was uniformly dispersed without having a concentration distribution.
[Comparative Example 5]
In Comparative Example 2, the same procedure was followed except that the hindered amine compound was changed to a 1: 3 (weight ratio) mixture of the hindered phenol compound Sumilizer MDP-9 (Sumitomo Chemical): Hindered amine LA-63P (Asahi Denka). Thus, a recording medium for ink was obtained. Moreover, it was found by the same IR measurement as in Example 1 that there was no concentration distribution, and the hindered amine compound and the hindered phenol compound were uniformly dispersed.

(A) And (B) is a figure which shows an example in connection with the subject of a prior art as a figure. (A) And (B) is a figure which shows an example in connection with the subject of a prior art as a figure. (A) And (B) is a figure which shows an example in connection with this invention as a figure. It is a figure which shows an example of the manufacturing method of the recording medium for ink concerning this invention as process drawing. It is a figure which shows an example of the manufacturing method of the recording medium for ink concerning this invention as process drawing. It is a figure which shows an example of the manufacturing method of the recording medium for ink concerning this invention as process drawing. FIG. 3 is a diagram illustrating a configuration of an ink recording medium according to the present invention. (A) And (B) is a figure which shows an example of the result in IR measurement. It is a figure which shows the light absorbency change in the depth direction of the ink receiving layer of a hindered amine compound.

Claims (15)

In a recording medium for ink comprising a recording surface and an ink receiving layer containing a pigment for holding an ink coloring material, a binder for the pigment, and a coloring material deterioration preventing material,
The ink receiving layer is within a range from the recording surface side to 30 μm in the depth direction, and the coloring material deterioration preventing material has a relatively high density part and a relatively low density part. And the high density part is located closer to the recording surface than the low density part.   The ink recording medium according to claim 1, wherein the coloring material deterioration preventing material is contained in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the pigment.   3. The ink recording medium according to claim 1, wherein the density of the highest density portion of the colorant deterioration preventing material contained in the ink receiving layer is 1.5 times or more of the density of the lowest density portion.   2. The density distribution of the color material deterioration preventing material decreases in the depth direction from the recording surface within a range of an upper region from the recording surface of the ink receiving layer to a depth of at least 15 μm. The recording medium for ink as described.   The density distribution of the coloring material deterioration preventing material decreases in the depth direction from the recording surface within a thickness range of 10 μm arbitrarily selected in the depth direction in the upper region. 4. A recording medium for ink according to 4.   The density distribution of the color material deterioration preventing material decreases in the depth direction from the recording surface within a thickness range of 5 μm arbitrarily selected in the depth direction in the upper region. 4. A recording medium for ink according to 4.   The ink receiving layer is coated with a coating solution containing alumina hydrate as the pigment, polyvinyl alcohol as the binder, and orthoboric acid as a crosslinking agent on a wet surface containing tetraborate. The ink recording medium according to claim 1, which is formed by processing.   The ink recording medium according to claim 1, wherein the colorant deterioration preventing material is a hindered amine compound. The ink recording medium according to claim 1, wherein the dry coating amount of the ink receiving layer is at least 30 g / m ² .   The ink recording medium according to claim 1, wherein the ink receiving layer is formed by coating on a liquid absorbent substrate. In a method for producing a recording medium for ink comprising a recording surface and an ink receiving layer containing a pigment for holding an ink coloring material, a binder for the pigment, and a coloring material deterioration preventing material,
In the depth direction from the recording surface side of the ink receiving layer, the color material deterioration preventing material includes a high density part having a relatively high density and a low density part having a relatively low density, and the high density part is A method for producing a recording medium for ink, comprising the step of forming, in the ink receiving layer, a concentration distribution of the color material deterioration preventing material positioned on the recording surface side with respect to the low concentration portion. In a method for producing a recording medium for an ink comprising a recording surface and an ink receiving layer comprising a pigment for holding an ink coloring material, a binder for the pigment, and a coloring material deterioration preventing material,
Forming a wet surface containing a cross-linking agent that cross-links the binder on the substrate, and forming an ink receiving layer by applying a coating liquid containing the pigment and the binder to the wet surface on the substrate When,
Applying a coating liquid containing the colorant deterioration preventing material from the surface of the ink receiving layer;
A method for producing a recording medium for ink, comprising: drying a coating liquid containing a coating material containing the coloring material deterioration preventing material in succession to form a distribution of the coloring material deterioration preventing material. .   The wet surface is formed by applying a pretreatment liquid containing the cross-linking agent on the substrate and then drying and solidifying it, and then applying a liquid containing the cross-linking agent to the treated surface. The method for producing a recording medium for ink according to claim 11 or 12, wherein the liquid surface is formed. The method for producing a recording medium for ink according to claim 11 or 12, wherein the pigment contains alumina hydrate, and the dry coating amount of the ink receiving layer is 30 g / m ² or more.   The method for producing a recording medium for ink according to claim 11, further comprising a rapid drying step of 100 ° C. or higher following the step of applying the coating material containing the colorant deterioration preventing material.

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